In recent years, various electronic products are being developed in the trend of easy operation, small size, and large screen. In particular, for portable electronic products, the requirements in volume and screen size are extremely strict. Thereby, many electronic products integrate the touch panel with the LCD panel in order to save the area required by keyboards or keypads and thus enlarging the disposable area on the screen.
Depending on their sensing principle, general touch panels can be categorized into resistive, capacitive, infrared, and ultrasonic types. Thanks to their advantages of dust repellence, scratch resistance, and high resolution, capacitive touch panels are increasingly adopted by electronic devices.
The principle of a capacitive touch panel is mainly to coat a layer of transparent conductive thin film, such as indium-tin oxide, on the surface of a glass substrate as the sensing structure. When a user touches the panel using his finger, the proximity of the finger changes the coupling capacitor of the sensing structure. Then the capacitive touch panel can determine the touched location by the finger according to the analysis of the capacitance variation in the sensing structure.
Nonetheless, a double-layer capacitive touch sensor requires disposing electrodes on the top and bottom surfaces of the glass substrate, respectively, and hence leading to the drawbacks of higher manufacturing costs and complicated processes. In order to solve the problems of the double-layer capacitive touch sensor, the single-layer capacitive touch sensor is developed.
The single-layer capacitive touch sensing structure according to the prior art is composed by two electrode groups. The first electrode group is composed by a first electrode and a second electrode only; the second electrode group is composed by a third electrode and a fourth electrode only. Thereby, it has only two touch locations, which limit its sensitivity. Besides, the shape of the first, second, third, or fourth electrodes is suitable for paired electrodes only, which disallows increase in the electrode number in each electrode group and hence enhancement in the sensitivity of touch sensing. In addition, the layout of its wires shrinks the area for the electrodes, making it is not possible to increase the sensitivity of touch sensing by disposing more electrodes in each electrode group. Thereby, there is still room for improvement for the single-layer capacitive touch sensing structure according to the prior art.
Accordingly, for solving the problems described above, the present invention provides a sensing structure of touch panel by using the shape of its electrodes and the layout of wires. Hence, two or more electrodes can be disposed in each electrode group for enhancing the sensitivity of touch sensing.